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Welcome again to our monthly newsletter
with features on exciting celestial events, product reviews, tips
& tricks, and a monthly sky calendar. We hope you enjoy it!
Geoff Gaherty's guide to finding interesting objects in the sky
if you don’t have (or don't want to use) computer assistance.
Constellation in Focus: Aquarius
Tricky targets this month: two planetary nebulas, three star
clusters, and one of the sky's best double-stars.
August issue I wrote about exploring the sky using the Orion
IntelliScope’s tour feature. But most telescopes aren’t
equipped with computerized tours to guide the beginner through the
sky. Here is a guide to finding interesting objects in the sky if
you don’t have computer assistance.
Seeing versus finding
There’s difference between finding the location of an
object and actually seeing it. Many of the objects we amateur
astronomers look at are too faint to be seen with the naked eye.
Some are too faint to be visible in our scope’s finder. Some may
be so faint as to be a challenge to see in the main telescope.
Seeing can be difficult. Finding an object, on the other hand,
involves pointing the telescope at exactly the spot in the sky
where the object is located. This can be done with a computer, or
manually using a technique called starhopping. It’s not necessary
to be able to see an object to point at it with the telescope.
Many beginners make the mistake of looking for objects
which are easy to find (because they are close to bright stars or
familiar constellations) but which are very hard to see, because
they are very faint. For example, many go hunting for the galaxy
Messier 101 in Ursa Major because it is located close to two
bright stars in the handle of the Big Dipper. Unfortunately, M101
is one of the most difficult objects in Messier’s catalog to see
because it is large in size and very faint, so its dim light is
spread over a large area. Unless you have very dark skies and a
trained eye, you can be staring right at M101 and never see it! So
it’s important, when you’re starting out, to go for objects which
are both easy to find (located near bright stars or
constellations) and also easy to see (bright clear objects, such
as double stars and star clusters). Leave the dim galaxies (for
the most part) until you have more experience.
Starhopping involves pointing your telescope using known
guideposts in the sky: bright stars and constellations. This in
turn requires some familiarity with the stars and their grouping.
When you first look up into a starry sky, especially from a dark
rural site, the view can be overwhelming. You wonder, “How will I
ever be able to make sense of all these stars?” Learning your way
around the starry sky is very much like learning your way around
an unfamiliar city. It helps to have a map. It helps to have a
familiar landmark or two to get your bearings. And it also helps
to have a friend to show you the way. For a map, you have software
which will give you an overview of the territory. You may know a
few “landmarks” in the sky to get you going, such as the Big
Dipper, Orion, a bright planet, or the Moon. An astronomical
friend is also very helpful in the early stages, someone who knows
the stars a bit better than you do and can point out some
landmarks. You may know such a person already, or you may need to
find one by joining a local astronomy club. Although I’m not out
there under the stars with you, I hope some of my suggestions here
will also help you get started.
The first step is to print out a chart or two to take
outside with you. Many of the charts you find in books or
magazines are less than helpful for two reasons: they try to show
all the sky, and they show it on too small a scale. I prefer to
use charts which show only part of the sky, but which are on a
large enough scale to approximate the actual spacing of the stars
across the sky.
For example, here’s a chart from Starry Night® showing a
section of sky roughly 90 degrees square, facing east at 8 pm on
Go out with this chart and face east. The top of the chart
is overhead, the bottom is the horizon. The most obvious object in
the eastern sky is Mars, glowing brightly about a third of the way
from horizon to overhead. But our targets for tonight are farther
away. As I said earlier, the Big Dipper is a poor starting place
for deep sky hunting because it lacks bright objects. Let’s look
instead at Cassiopeia, a constellation which lies almost directly
opposite the Big Dipper in the northern sky. In this chart, it's
about two thirds of the way from horizon to zenith, an obvious
lopsided W shape, visible even under city skies. Once you’ve
identified Cassiopeia, you have some landmarks which will let you
point your telescope at a variety of interesting objects.
Here’s a more detailed chart of the Cassiopeia, made by
zooming in with Starry Night®:
Besides your star chart, you will need a
red flashlight to read it. You will also find it very helpful
to have a pair of binoculars with a field of view similar to that
of the finder scope on your telescope. I
10x50 binoculars particularly useful for this. Binoculars let
you practise the “hop” in a more natural way than the view through
the telescope’s finder, which is usually upside down. After I’ve
tried a “hop” a few times with binoculars, I’m ready to repeat it
with the telescope finder.
Two double stars
Let’s start by tracking down a couple of double stars. Many
beginners are unaware that many of the stars which appear single
to our naked eyes are double or multiple in a telescope. They are
great targets for beginners because they are easy to see as well
as easy to locate.
The five bright stars in Cassiopeia which mark the W are
named, from top to bottom in this view: Beta β, Alpha α, Gamma γ,
Delta δ, and Epsilon ε. We can find our first double star, Eta η
Cassiopeiae, by looking a little less than half way between stars
Alpha α and Gamma γ. You can see it there in the chart below,
marked by the Greek letter Eta η. Place the crosshairs in the
finder of your telescope on that star, and when you look through
the telescope you will see it is actually two stars: a bright
yellow one and a fainter red one.
The second double star is a bit farther afield, but
illustrates the principles of starhopping. Look at the two top
stars of the W, Beta β and Alpha α. Use the distance between these
two stars as your “measuring stick.” Extend the line from Beta to
Alpha by two stick lengths to the lower right, which will take you
to the star 51 Andromedae. Continue in the same direction about
half the distance again, and you will reach a brighter star, Gamma
γ Andromedae. This is our target: in the telescope it will appear
as a double star, the two stars a bit closer than Eta η
Cassiopeiae, and this time colored gold and blue.
Four star clusters
Now let's go after some deeper targets, some of the
beautiful star clusters located in or near Cassiopeia. First take
a close look at Delta δ Cassiopeia (second from the bottom in the
W). In binoculars you will see a fairly bright star below and to
the right of it, Chi χ Cassiopeiae. Use the line between Delta and
Chi as the base of an equilateral triangle hanging below them, and
put the crosshairs of the finder on the lower angle of this
triangle. Through the telescope’s eyepiece you will see a compact
little star cluster, number 103 in Messier’s catalog. Imagine a
tall thin isosceles triangle on the opposite side of the same
baseline, put your crosshairs there, and through the telescope you
will see the star cluster NGC 457. It has two bright stars in it
which many people see as eyes. Traditionally those are the eyes of
an owl, the rest of the cluster forming the erect body of the owl
with wings outstretched. But to our modern eyes, it looks rather
like the character E.T. in the famous movie. So this cluster is
called by some the Owl Cluster and by others the E.T. Cluster!
Let’s go hunting farther away. This time use the line
joining Gamma and Delta Cassiopeia as your measuring stick and
pointer. Go twice its length downward towards the horizon and you
should see a fuzzy patch through your binoculars and finder.
Through the telescope you will see the Double Cluster in Perseus,
one of the wonders of the night sky in any telescope. If you keep
going in the same direction towards the horizon you will encounter
a line of three bright stars, the last of which is at the center
of a little known star cluster, Melotte 20. The trouble with this
cluster is that it is so close to us that its stars are spread
wide across the sky, too wide to fit in most telescopes, so that
they can only be viewed with binoculars or the naked eye. This is
one of the star clusters closest to our Sun, also called the Alpha
Persei Moving Cluster because the star Alpha α Persei is at its
center, and all the stars share a common proper motion across the
And a galaxy
Now that you’ve become better trained in starhopping, I’m
going to end by giving you a special treat. I said earlier that
most galaxies are difficult for beginners to see, but one
exception is the Andromeda Galaxy, quite close to Cassiopeia.
Here’s how to find it. Look closely at the top three stars of
Cassiopeia, Beta, Alpha, and Gamma. If you look closely, you’ll
see that there’s a fourth star, Kappa κ Cassiopeiae forming a
rather lopsided square with the three brighter stars. Use the line
from Kappa to Alpha as your measuring stick, and follow the line
from Kappa to Alpha two and a half lengths to the right. Through
binoculars and your finder you should see a faint fuzzy patch.
Through the telescope you will see a much larger fuzzy patch.
Don’t expect to see its spiral arms or much else (unless you have
very dark skies and a large telescope), but be aware that the
light you are seeing is coming from more than two million light
years away—that’s part of the magic of astronomy!
Geoff has been a life-long telescope addict, and is active in many
areas of visual observation; he is a moderator of the Yahoo
"Talking Telescopes" group.
[Top of Page]
The Saturn Nebula (NGC 7009) is an oval Mag 8 fuzzy
patch hanging in space about 4,000 lightyears distant.
Medium-sized scopes show a ring with "knobs" on either side.
M72, close by, is a small remote globular cluster,
difficult to resolve. The open cluster M73 is a tiny
triangular collection of stars, barely noticeable. However, the
same field of view contains a lovely Lyra-like asterism.
The Mag 7 globular cluster M2 is about 40,000
lightyears away. Although among the brightest of globs in the sky,
M2's core is so concentrated that, as an observational object, it
ranks as one of the less compelling.
The Helix Nebula (C63/NGC 7293) is a tricky target.
Although it is the largest visible planetary in the night sky
(about half the apparent diameter of the full moon) it's quite
dim. Dark skies are a must. A low power eyepiece in your
telescope, with averted vision, may give you some hint of
Finally, 103 lightyears distant is one of the sky's finest
doubles, Zeta Aquarius.
Sean O'Dwyer, Starry Night® Times Editor
[Top of Page]
Space Probe Video
Watch interplanetary space probes as they
visit the planets and moons of our solar system in this 2 1/2
minute video clip created with Starry Night® version 5.7.
5.7 update if you're already a 5.x user or
upgrade if you own version 4.x or earlier, and create your
own space movies!
Probe Movie 204 [4.3 MB]
Trouble viewing? You'll need
QuickTime 7 to
view this movie.
Saturday, October 29
Mars and Earth are just 43,000,000 miles apart
Tuesday, November 1
New moon at 8:25 PM
Thursday, November 3
Mercury and Venus are both at greatest eastern elongation
Monday, November 7
3AM, Mars is at opposition
Tuesday, November 8
First quarter moon
Tuesday, November 15
1 AM, a full moon passes 3° north of Mars
Thursday, November 17
Leonid meteor shower peaks before dawn
Wednesday, November 23
Last quarter moon
All times shown are U.S. Eastern Time.